/**
 *    Copyright (C) 2013-2014 MongoDB Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include "mongo/db/diskloc.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/query/canonical_query.h"

namespace mongo {

    /**
     * A standalone stage implementing the fast path for key-value retrievals
     * via the _id index.
     */
    class IDHackStage : public PlanStage {
    public:
        /** Takes ownership of all the arguments -collection. */
        IDHackStage(OperationContext* txn, const Collection* collection,
                    CanonicalQuery* query, WorkingSet* ws);

        IDHackStage(OperationContext* txn, Collection* collection,
                    const BSONObj& key, WorkingSet* ws);

        virtual ~IDHackStage();

        virtual bool isEOF();
        virtual StageState work(WorkingSetID* out);

        virtual void saveState();
        virtual void restoreState(OperationContext* opCtx);
        virtual void invalidate(const DiskLoc& dl, InvalidationType type);

        /**
         * ID Hack has a very strict criteria for the queries it supports.
         */
        static bool supportsQuery(const CanonicalQuery& query);

        virtual std::vector<PlanStage*> getChildren() const;

        virtual StageType stageType() const { return STAGE_IDHACK; }

        PlanStageStats* getStats();

        virtual const CommonStats* getCommonStats();

        virtual const SpecificStats* getSpecificStats();

        static const char* kStageType;

    private:
        // transactional context for read locks. Not owned by us
        OperationContext* _txn;

        // Not owned here.
        const Collection* _collection;

        // The WorkingSet we annotate with results.  Not owned by us.
        WorkingSet* _workingSet;

        // The value to match against the _id field.
        BSONObj _key;

        // Did someone call kill() on us?
        bool _killed;

        // Have we returned our one document?
        bool _done;

        // Do we need to add index key metadata for $returnKey?
        bool _addKeyMetadata;

        CommonStats _commonStats;
        IDHackStats _specificStats;
    };

}  // namespace mongo
